1. Field of the Invention
The present invention is directed to a low profile electrical connector assembly, and more particularly to a combination of surface mountable socket and plug.
2. Description of the Prior Art
U.S. Pat. No. 5,626,482 discloses a surface mountable electrical connector composed of a socket with a plurality of first terminals and a plug with a plurality of second terminals for mating contact with the first terminals. Each of the first terminals has a U-shaped portion to provide a first spring contact end at one of opposed legs of the U-shaped portion. While, each of the second terminal is shaped to have a rather straight contact end for pressed contact with the first spring contact end. The structure relies upon the spring force substantially only from a resilient deformation of the U-shaped portion on the side of the first terminal to achieve the pressed contact. In order to maintain a reliable contact between the terminals with this structure, it is necessary to make the U-shaped portion develop a considerably large spring bias. In this consequence, however, the structure requires a correspondingly large operating force to insert or remove the plug into and from the socket against the spring bias of the U-shaped portion for electrical engagement and disengagement between the first and second terminals. Otherwise, poor electrical contact would result. Further, the straight contact end of the second terminal is required to be held to a dielectric plug base over a long length so as to be firmly fixed thereto, thereby add an extra height to the plug and therefore the assembly of the plug and the socket, which is a hindrance to achieving a low profile design of the assembly.
Although not relating to the structure of the contact terminals, the above-mentioned patent discloses a structure of detachably connecting the plug and the socket with the use of two complementary U-shaped spring members fixed respectively to the socket and the plug. These two U-shaped members are incorporated to hold the plug and socket in mated condition and are therefore provided with no terminal lead for electrical connection with electrical circuits of printed board on which the socket and plug are mounted. Thus, the two U-shaped members are positioned without considering the effect of achieving a suitable contacting pressure and an arrangement of the terminal leads. Even if the two U-shaped spring members would be utilized to the first and second terminals, i.e., the straight contact end of the second terminal is modified to have the U-shaped portion, while keeping the terminal leads of the first and second terminals in suitable positions for the surface mounting, it would be necessary to orient the two U-shaped portion in the opposite directions in the assembled condition, as schematically shown in FIG. 1. However, such modified structure cannot permit to give a contact point at the interface between the free ends of the mating legs, and only permit to give the contact point away from the free end of one of the mating legs. With this result, substantially only one of the U-shaped portions is best utilized to give a spring bias for providing a contact pressure between the first and second spring contacts. Therefore, the modification is still insufficient in making the best use of the two U-shaped portions respectively of the first and second terminals to give a maximum contact pressure for reliable electrical connection between the first and second terminals.